Why are My Dog’s Eyes Red?

Your dog’s eyes are as sensitive as your own, and as susceptible to irritation, allergies, injury, and disease. One of the earliest, surest signs of irritation is red eyes. If your dog’s eyes appear visibly red or swollen, it could be a sign of something as minor as an irritation or mild allergy, or as serious as eye disease.

Read on to learn more about your dog’s eyes, what makes them red, when red eyes are a sign that you should go to the vet, and how you (and your vet) can take care of your pup’s peepers.

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Why Dogs’ Eyes are Sensitive

Dog eyes have a lot in common with your own: the eye is an active organ, constantly adjusting to light and focusing on objects in the environment. All the parts of the eye work together to produce images and relay them to the brain.

Dogs’ eyes differ from humans in that they have a third eyelid, the nictitating membrane, located in the inside corner of the eye. The third eyelid will extend up to protect the eyeball from scratches, or in response to inflammation. Dogs also have more rods in their corneas than humans do, which means they track light and movement better than you can (but overall their vision is less acute, and they don’t see as wide a range of colors).

As is the case with your eyes, external irritants can cause irritation, and disease can weaken or damage specific parts of your dog’s eye. Some types of dogs are more prone to eye issues than others, including:

Brachycephalic, or flat-faced, breeds like bulldogs, shih tzus, and pugs

Breeds with long hair around their faces, like poodles, maltese, and sheepdogs

Older dogs, or dogs with existing health problems such as high blood pressure or diabetes

Causes of Red Eyes in Dogs

Redness, swelling, and discharge can indicate a wide array of issues for dogs, from harmless, mild allergies to something far more serious.

Some of the most common causes of red, bloodshot, and/or weepy eyes in dogs include:

Eye injury or trauma, such as a scratch or foreign object in the eye

Allergies (to food or environmental agents)

Conjunctivitis, also known as “pinkeye” or “red eye.” An itchy inflammation of the tissue coating the eye, pinkeye is as common in dogs as it is in humans, and typically affects one eye at a time (source)

Glaucoma, a fluid build-up in the eye that creates pressure which, if not alleviated, can cause blindness. Redness caused by glaucoma will be accompanied by visible swelling; learn more here.

Dry eye syndrome (formally known as Keratoconjunctivitis sicca, or KCS). Dry eye can be caused by a number of underlying illnesses, so it’s important to have your dog checked out by a vet!

Uveitis, a painful inflammation of certain parts of the eyeball

Corneal ulcers, an erosion of the transparent, shiny membrane that makes up the front of the eyeball. Corneal ulcers are typically caused by trauma, such as getting scratched while running through brush.

Red eyes can also be caused by underlying medical issues like hyperthyroidism, diabetes, and some cancers. Of course, sometimes a red eye is simply a temporary reaction to a mild irritant! If you notice your dogs’ eyes look unusual, remain calm and consult a professional.

When Should You Take Your Dog to the Vet for Eye Care (and What the Vet will Do)

Red eyes aren’t always a sign of something bad, but eye injury and disease can progress rapidly, so it’s better to be safe than sorry. If you see something new and unusual in your dogs’ eyes, if she’s scratching or rubbing her face, and/or if you notice discharge or squinting, it’s time to call the vet.

When you take your dog to the vet for eye care, the vet may do some or all of the following:

Conduct a complete ophthalmologic exam, examining all the structures of your pet’s eye. This is the part where they may track your dog’s vision by holding an object in front of them and moving it around, and look inside the eye with an ophthalmoscope, as pictured above.

Schirmer tear test to determine if your dogs’ eyes are lubricating properly. This test uses small strips of paper held in place in the lower eyelid; it’s a bit uncomfortable, but not painful!

Test the internal pressure of your dog’s eye using a tool called a tonometer

Fluorescein stain test, which uses a harmless dye applied to the eye, allowing your vet to see otherwise-invisible scratches and corneal injuries

Blood tests: Your vet may choose to run a blood screening in order to find underlying medical issues and illnesses that can cause eye issues.

Many eye problems can be treated with topical and/or oral medications. However, if there is a more serious underlying cause for your dog’s red eyes, the vet may refer you to a veterinary ophthalmologist for more tests and treatment.

How to Keep Your Dog’s Eyes Healthy

You can’t protect your dog from every possible eye irritant, injury, or illness; after all, dogs are gonna dog! But you can take preventative measures to keep your pooch’s eyes as healthy and protected as possible:

For long-haired breeds, keep the hair around their eyes trimmed and clean.

Clean gunk away from your dogs’ eyes as needed (with a damp tissue or cotton ball, gently wipe from the inside corner to the outside, being careful not to touch the eyeball)

Watch your dog for excessive eye rubbing or scratching, which can be a sign of something amiss

As cute as it can be when a dog hangs their head out the window of the car, this is actually a leading cause of eye injury. Keep the windows rolled up enough so they can’t fit their heads out, or invest in a pair of doggles before your next road trip.

Regular veterinary exams (once a year for a young adult dogs; twice a year for your senior buddy)

As with any dog health issue, when it comes to eye care, the important thing is to pay attention to your dog. You can tell a lot just by looking at them, and noticing changes in their appearance, body language, and behavior. And of course, remember to take time to gaze lovingly into your dog’s eyes; it may not be scientifically proven to improve eye health, but it’s a great way to bond with your best friend!